In known release ski bindings of this type, the holding spring, having adjustable pre-tension, has sufficient holding power normally to hold the ski boot in the binding and thus on the ski. This holding power is usually of virtually constant magnitude. As soon as the ski boot receives a stress through the lower leg portion or ankle or foot of the skier, which stress occurs for example due to a fall, and is able to overcome the holding force, the binding releases and sets the ski boot free.
Lately more release bindings have become known in which the release takes place substantially independent of, or dependent only to a predetermined degree upon, the type or the direction of the stress which the boot experiences. Thus, an important step in the direction of an ideal safety ski binding has already been taken in which -- the correct adjustment of the holding spring or springs being assumed -- the desired goal consists in offering a high level of security against breaks because of excessive stress on the skier's legs during skiing.
In the same direction are devices which bring the release, namely the overcoming of the holding force, into a selectable relationship to the time pattern by which the stress is applied to the ski boot. This direction of development prevents a release in the case of suddenly rising and immediately falling stress, even though the peak value is of itself sufficient to overcome the holding force. Especially in the case of high speed skiing, and the hard and quick impacts onto the ski which inevitably result therefrom, it is possible with this type of construction to prevent a premature and undesired release of the binding, it being well known that the premature and undesired release of the ski binding also often leads to falls and to resultant injuries.
The known release ski bindings, however, do not consider certain anatomical realities of the human legs. These are comparable -- expressed in a greatly simplified manner -- with a jointed linkage, in which between the individual link members (bones) there are provided joints (bone joints held together by ligaments), which permit a pivoting and also somewhat of a folding of the link members with respect to one another.
The natural movability of the bones with respect to one another is limited by two natural limit positions. Upon exceeding these limit positions injuries occur, for example, pulling of ligament pullings and breaking of joints, joint members or bones.
Especially in the area of the foot angle system which during skiing is probably stressed the most aside from the knee or hip joint, it is important which instantaneous position the foot joint system occupies when a possibly serious stress occurs. In other words: If the joint is, because of an intended position or because of a position existing because of the skiing position, near one limit position with respect to twisting and/or inclination of the lower leg portion in relation to the foot, a considerably small extra stress in direction of the limit position is sufficient to cause an injury. However, if the joint is approximately in a central position between the limit positions, then such a stress does not cause danger of injury because the foot can still yield.
Accordingly the purpose of the invention is to produce a release ski binding of the above-discussed type which takes into account the aforementioned facts in that the holding force receives an anticipatory control which depends upon the respective position of the foot joint system. This results in that the closer the foot joint system comes to one of its natural limit positions, the more is reduced the stress which is required for overcoming the holding force.